[Python-ideas] Fwd: Re: doctest

Guido van Rossum guido at python.org
Sat Feb 18 05:55:48 CET 2012

On Fri, Feb 17, 2012 at 8:25 PM, Ian Bicking <ianb at colorstudy.com> wrote:
> On Feb 17, 2012 3:58 PM, "Mark Janssen" <dreamingforward at gmail.com> wrote:
>> I find myself wanting to use doctest for some test-driven development,
>> and find myself slightly frustrated and wonder if others would be
>> interested in seeing the following additional functionality in
>> doctest:
>> 1. Execution context determined by outer-scope doctest defintions
>> 2. Smart Comparisons that will detect output of a non-ordered type
>> (dict/set), lift and recast it and do a real comparison.
>> Without #1, "literate testing" becomes awash with re-defining re-used
>> variables which, generally, also detracts from exact purpose of the
>> test -- this creates testdoc noise and the docs become less useful.
> I dunno... I find the discipline of defining your prerequesites to be a
> helpful feature of doctest (I find TestCase.setUp to be smelly).  You can
> include a namespace in doctest invocations, but I'm guessing the problem is
> that you aren't able to give these settings when using some kind of test
> collector/runner?  More flexible ways of defining doctest options (e.g.,
> ELLIPSIS) would be helpful.
>> Without #2, "readable docs" nicely co-aligning with "testable docs"
>> tends towards divergence.
> IMHO this could be more easily solved by replacing the standard repr with
> one that is more predictable.  At least that would handle dictionaries, it
> becomes a bit more difficult for custom types.  Also it diverges from being
> exactly like the console, but eh, I don't think that's a big advantage.
> Unfortunately plugging in a custom repr is kind of hard; Python has a way to
> specifically compile expressions into "print repr(expr)" (more or less) but
> no general way to get the value of expressions (while also handling
> statements).  But if you wanted to try it, I did figure out a terrible hack
> for it.

Isn't sys.displayhook() usable for this purpose?

--Guido van Rossum (python.org/~guido)

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